- Constrained mate choice in social monogamy means that many individuals wind up with unattractive partners.
- "Unattractiveness" is likely tied to genetic compatibility, which can include behavior factors.
- Females paired with unattractive males have increased stress hormone levels, which may drive cheating and breakups.
In socially monogamous species, from birds to humans, most individuals find partners.
A large proportion of females, however, wind up with unattractive males of below-average quality, according to a new study that also found such less-than-ideal relationships raise female stress levels.
The findings negate prior theories that, in monogamous species throughout the animal kingdom, each female has a good chance of pairing with a male that matches her ideal choice of partner.
"In socially monogamous animals, very few individuals end up with the perfect partner because, of course, he or she is likely to be paired to someone else. That is, lots of men would like to be married to, say, Angelina Jolie, and lots of women would love to be married to Brad Pitt. But the reality is that they can't and only someone like Brad Pitt is able to marry someone like Angelina Jolie," lead author Simon Griffith told Discovery News.